| I've heard of this. And here is what Wikipedia has to say about it:
In music, the BACH motif is the sequence of notes B flat, A, C, B natural. Bach's use of this cruciform melody in reference to himself extended to its inversion, retrograde, retrograde-inversion, and all transpositions thereof.
This four-note motif has been used by a number of composers, usually as a homage to Johann Sebastian Bach. The first known example, however, is in a piece by Jan Pieterszoon Sweelinck in the 17th century.[citation needed] The possibility of being able to spell the surname Bach in this way comes about because, in German, B indicates what in English is called B flat, while H indicates what in English is called B natural.
BACH signature cross, used to depict the motif at least as early as the 19th century, but not known to have been used by Bach himself
J. S. Bach himself used it as a fugue subject in the final part of Die Kunst der Fuge (BWV 1080), a work he did not complete before he died in 1750. It appears in passing in several of his other pieces, such as at the end of the fourth and fifth of the canonic variations on "Vom Himmel Hoch", BWV 769. Its appearance in the penultimate bar of the Kleines harmonisches Labyrinth, BWV 591, is not thought to be very significant and the work may even be spurious (Johann David Heinichen has been suggested as a possible composer). It shows up in the St Matthew Passion in the section where the chorus sings "This man was God's own son most truly." In many pieces, while the exact notes B-A-C-H are not played, a transposition of the motif is used (a note sequence with the same intervals: down a semitone, up a minor third, down a semitone). Many of the fugues in Bach's Well-Tempered Clavier, for example, employ the motive in transposed form.
A fugue for keyboard in F major by one of Bach's sons, probably either Johann Christian Bach or Carl Philipp Emanuel Bach, exists using the motif, but it was not until the 19th century when interest in Bach was revived that the motif began to be used with any regularity.
Perhaps because it was used by Bach himself in a fugue, the motif is often used by other composers in fugues or other complex contrapuntal writing. | 
